mid- ocean ridge: the longest chain of mountains in the world.
sonar: a device that bounces sound waves of underwater objects and then records the echoes of these sound waves.
sea- floor spreading: the process that continually as new material to the ocean floor.
deep- ocean trenches: a deep under- water canyon.
subduction: the process by which the ocean floor sinks back into the mantle.
Outline
Mapping the Mid- Ocean Ridge
in the mid 1900's scientists mapped the mid- ocean ridge using sonar.
it extends through all the world oceans.
most mountains that are in the mid- ocean ridge lie under water, but in some places the ridge pokes above the surface.
Evidence for Sea- Floor Spreading
a man named Henry Hess, an American geologist, studied the mid- ocean ridge and carefully studied maps of the mid- ocean ridge.
evidence from molten material
rock shaped like pillows and toothpaste
evidence from magnetic strips
iron lined magnetic pole
evidence from drilling samples
youngest rock near center of ridge, the older the more far away
Subduction at Deep- Ocean Trenches
deep- ocean trenches subducts the ocean floor
ocean floor sinks back into the mantle
Subduction and Earth's Oceans
ocean floor renewed every 200 million years subduction in the Atlantic and Pacific ocean
Pacific ocean covers one third of the planet but is shrinking
Table of Contents
Section 4 (1-4) Sea- Floor Spreading
Vocabulary
mid- ocean ridge: the longest chain of mountains in the world.
sonar: a device that bounces sound waves of underwater objects and then records the echoes of these sound waves.
sea- floor spreading: the process that continually as new material to the ocean floor.
deep- ocean trenches: a deep under- water canyon.
subduction: the process by which the ocean floor sinks back into the mantle.
Outline
Mapping the Mid- Ocean Ridge
Evidence for Sea- Floor Spreading
Subduction at Deep- Ocean Trenches
Subduction and Earth's Oceans